This invention relates to aquarium filters, and more particularly to an external aquarium filter having a mechanism for controlling the flow rate of aquarium water from an aquarium tank into the filter, between a maximum flow rate and a substantially shut-off flow rate.
Aquarium filters are generally utilized for aeration and filtration of aquarium water and at the same time provide a circulation to such water. One type of aquarium filter commonly in use is an externally mounted filter having a housing which is mounted on the wall of an aquarium tank.
One such aquarium filter assembly is described in U.S. Pat. No. 4,512,885, and assigned to the assignee of the present invention. Such aquarium filter assembly includes a housing unit which is adapted to be mounted externally on a wall of an aquarium tank. The housing unit contains an intake chamber which receives contaminated water from the aquarium tank, and a filter chamber for filtering the contaminated water from the intake chamber. The two chambers are in fluid flow communication with each other. A removable unitary intake assembly is supportedly positioned in the housing and includes an inlet flow tube for supplying the contaminated water from the aquarium tank to the intake chamber, and a pump impeller unit which is magnetically coupled to a motor unit. The motor unit is externally supported from the housing unit and includes stator laminations having an interior bore. The pump impeller unit is mounted on a rotor and extends from the inlet flow tube into the bore for magnetic coupling to the stator laminations.
In operation, the filter is initially primed by placing water in the intake chamber sufficient to cover the impeller unit. The filter assembly is mounted on the aquarium tank wall with the inlet flow tube extending into the aquarium tank water. The motor is energized to rotate the impeller causing a reduced pressure at an outlet end of the unitary intake assembly. The reduced pressure causes the aquarium tank water to flow through the intake assembly into the intake chamber of the filter through a centrifugal pumping action. As the water accumulates in the intake chamber of the filter assembly, it flows into the filter chamber where the contaminated water is filtered and discharged back into the aquarium tank.
In using an aquarium filter assembly of the aforementioned kind, it is desirable to control the flow rate of water from the aquarium tank into the filter. Normally, the flow is constant and dependent upon the strength of the impeller unit. However, such constant flow rate may be too much for specific activities of the aquarium tank. For example, when adding food to the tank, it is desirable to reduce the flow rate since a strong flow would draw in the food into the filter and prevent its consumption by the fish. At the same time the food in the filter would tend to overload the filter unit itself. By reducing the flow rate to a minimum, the food will have an opportunity to be dissipated in the tank and consumed by the fish.
Likewise, when adding baby fish, a continuous heavy flow rate of water from the tank may cause complications to the tank and thus a reduced flow rate would be desirable. A control valve is therefore needed for the aforementioned aquarium filter assembly. Such control valve could be included within the intake assembly unit as is described in the aforementioned patent. An additional type of control valve is described in U.S. Pat. No. 4,602,996 also assigned to the assignee of the present invention. In this latter control valve, an adjustable valve member is disposed in one of the legs of the intake assembly unit for controlling the rate of flow and is manually operable externally of the filter unit. The valve member includes an elongated tube having one closed portion and one open portion and is rotatable within one of the legs of the intake assembly unit where it can substantially reduce the flow of water from the aquarium tank.
While such prior art control valves are useful in the intake assembly, the construction of such valves adds considerable cost to the manufacture of the intake unit assembly and requires substantial modification of molds. Additionally, during use of such valves, the valve can reduce the flow rate but normally does not shut off the flow rate. Normally, shutting off of the flow rate will stop all flow into the intake assembly. Since the motor unit continues operating it heats whatever water is in the intake chamber. Such continued heating of the water may evaporate the water in the intake chamber and without any flow of water to cool the motor the heat may cause damage to the surrounding parts. Additionally, complete evaporation of the water will then require new re-priming of the intake chamber upon resumption of filter operation upon opening the valve. Accordingly, with prior art valves it was preferably not to completely close down the valve and to only utilize the control valve for a reduction of the flow from a maximum to a reduced flow rate.